Nonlinear Optical Chromophores Having Tetrahydrocarbazole Donor Groups, Lyotropic Compositions Containing the Same, and Methods of Poling Such Compositions

ABSTRACT

Nonlinear optical chromophore compositions which display lyotropic nematic liquid crystal phases in polar organic solvents and provide a mechanical anisotropic effect allowing for the formation of a non-centrosymmetric chromophore-polymer matrix without the application of an electric field.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Pat. ApplicationNo. 63/288,089, filed Dec. 10, 2021, the entire contents of which arehereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

Nonlinear optical (NLO) chromophores provide the electro-optic (EO)activity in poled, electro-optic polymer devices. Electro-optic polymershave been investigated for many years as an alternative to inorganicmaterials such as lithium niobate in electro-optic devices.Electro-optic devices may include, for example, external modulators fortelecom, datacom, RF photonics, and optical interconnects and so forth.Polymeric electro-optic materials have demonstrated enormous potentialfor core application in a broad range of next-generation systems anddevices, including electro-optic modulators, optical switches, phasedarray radar, satellite and fiber telecommunications, cable television(CATV), optical gyroscopes for application in aerial and missileguidance, electronic counter measure (ECM) systems, backplaneinterconnects for high-speed computation, ultraquick analog-to-digitalconversion, land mine detection, radio frequency photonics, spatiallight modulation and all-optical (light-switching-light) signalprocessing.

Many NLO molecules (chromophores) have been synthesized that exhibithigh molecular electro-optic properties. The product of the moleculardipole moment (µ) and hyperpolarizability (β) is often used as a measureof molecular electro-optic performance due to the dipole’s involvementin material processing. See Dalton et al., “New Class of HighHyperpolarizability Organic Chromophores and Process for Synthesizingthe Same”, WO 00/09613.

Nevertheless, extreme difficulties have been encountered translatingmicroscopic molecular hyperpolarizabilities (β) into macroscopicmaterial hyperpolarizabilities (χ²). Molecular subcomponents(chromophores) must be integrated into NLO materials that exhibit (i) ahigh degree of macroscopic nonlinearity and (ii) sufficient temporal,thermal, chemical, and photochemical stability. High electro-opticactivity and the stability of electro-optic activity, which is alsoreferred to as “temporal stability,” are important for commerciallyviable devices. Electro-optic activity may be increased in electro-opticpolymers by increasing the concentration of nonlinear opticalchromophores in a host polymer and by increasing of the electro-opticproperty of chromophores. However, some techniques for increasingchromophore concentration may decrease poling efficiency and temporalstability. Simultaneous solution of these dual issues is regarded as thefinal impediment in the broad commercialization of EO polymers innumerous devices and systems.

The production of high material hyperpolarizabilities (χ²) is limited bythe poor social character of NLO chromophores. Commercially viablematerials must incorporate chromophores at large molecular densitieswith the requisite molecular moment statistically oriented along asingle material axis. In order to achieve such an organization, thecharge transfer (dipole) character of NLO chromophores is commonlyexploited through the application of an external electric field duringmaterial processing that creates a localized lower-energy conditionfavoring noncentrosymmetric order. Unfortunately, even at moderatechromophore densities, molecules form multi-molecular dipolarly-bound(centrosymmetric) aggregates that cannot be dismantled via realisticfield energies. To overcome this difficulty, integration of anti-socialdipolar chromophores into a cooperative material architecture iscommonly achieved through the construction of physical barriers (e.g.,anti-packing steric groups) that limit proximal intermolecularrelations.

Thus, it has often been considered advantageous in the art to producenonlinear optical chromophore containing materials that exhibit a highglass transition temperature (Tg). Materials with a high glasstransition temperature exhibit improved thermal stability and maintaintheir macroscopic electro-optic properties to a greater degree thanmaterials with lower glass transition temperatures. However, materialswith such elevated glass transition temperatures require significantlyincreased temperatures during poling processes to achieve adequatealignment. The necessity of employing such elevated temperatures iscostly, time-consuming and results in poling inefficiency.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed, in general, to nonlinear opticalchromophores which form lyotropic mixtures in a solvent and exhibitliquid crystalline properties. Various embodiments of the presentinvention can thus provide improved poling efficiency.

Various embodiments of the invention exhibit liquid crystallineproperties and form lyotropic compositions when mixed with a solvent.For example, in certain embodiments, the chromophores display lyotropicnematic liquid crystal phases in polar organic solvents. Resultingliquid crystalline properties provide a mechanical anisotropic effectallowing for the formation of a non-centrosymmetric chromophore-polymermatrix without the application of an electric field. In accordance withvarious embodiments described herein, a sufficient electro-opticcoefficient (r₃₃) can be induced mechanically, alleviating the need forthe application of poling temperature and electric field, typically 170°C. & 100 v/pm. The liquid crystalline properties and the lyotropiccompositions allow for milder processing conditions and, thus, higherpoling efficiency

Various embodiments according to the present invention include anonlinear optical chromophore of the general formula (I):

wherein D represents an organic electron-donating group; A represents anorganic electron-accepting group having an electron affinity greaterthan the electron affinity of D; and II represents a II-bridge between Aand D; wherein the electron-donating group D comprises atetrahydrocarbazole moiety bound to the II-bridge at a carbon atom inthe tetrahydro six-membered carbon ring of the tetrahydrocarbazolemoiety, and wherein the hydrogen bound to the nitrogen of thefive-membered ring of the carbazole moiety is replaced with asubstituent R.

Various embodiments according to the present invention include alyotropic composition comprising a nonlinear optical chromophore of thegeneral formula (I) and a solvent.

Various embodiments according to the present invention include a thinfilm formed from a composition as disclosed herein. Various embodimentsaccording to the present invention include an electro-optic deviceincluding a thin film as disclosed herein.

Other aspects, features and advantages will be apparent from thefollowing disclosure, including the detailed description, preferredembodiments, and the appended claims.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofpreferred embodiments of the invention, will be better understood whenread in conjunction with the appended drawings. For purposes ofillustration the invention, there are shown in the drawings embodimentswhich are presently preferred. It should be understood, however, thatthe invention is not limited to the precise arrangements andinstrumentalities shown.

In the drawings:

FIG. 1 is a graphical representation of light absorption of achromophore in accordance with an embodiment of the invention inlyotropic phase and after solvent removal;

FIG. 2 a is a polarized light microscopy image of a chromophore inaccordance with an embodiment of the invention forming micelles insolvent;

FIG. 2 b is a polarized light microscopy image of a chromophore inaccordance with an embodiment of the invention after shear alignmentexhibiting red shift; and

FIG. 2 c is a polarized light microscopy image of a chromophore inaccordance with an embodiment of the invention after removal of thesolvent.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, the singular terms “a” and “the” are synonymous and usedinterchangeably with “one or more” and “at least one,” unless thelanguage and/or context clearly indicates otherwise. Accordingly, forexample, reference to “a solvent” or “the solvent” herein or in theappended claims can refer to a single solvent or more than one solventor mixture thereof. As a further example, and not limited to onlyelectron-donating groups, reference to “an electron-donating group” or“the electron-donating group” herein or in the appended claims can referto a single electron-donating group or more than on electron-donatinggroup (e.g., “D” in any molecular formula herein may represent two ormore electron-donating groups both bound to the II-bridge).Additionally, all numerical values, unless otherwise specifically noted,are understood to be modified by the word “about.”

As used herein, the term “nonlinear optical chromophore” (NLOC) refersto molecules or portions of a molecule that create a nonlinear opticeffect when irradiated with light. The chromophores are any molecularunit whose interaction with light gives rise to the nonlinear opticaleffect. The desired effect may occur at resonant or nonresonantwavelengths. The activity of a specific chromophore in a nonlinear opticmaterial is stated as its hyper-polarizability, which is directlyrelated to the molecular dipole moment of the chromophore. The variousembodiments of NLO chromophores of the present invention are usefulstructures for the production of NLO effects.

Nonlinear optical chromophores in accordance with various embodiments ofthe invention exhibit liquid crystalline properties and form lyotropiccompositions when mixed with a solvent. Nonlinear optical chromophoresin accordance with various embodiments of the invention exhibit highglass transition temperatures and self-alignment forming J-aggregateswhen combined with solvents to form lyotropic compositions, as opposedto head-to-tail alignment exhibited in the art (i.e., H-aggregates).Nonlinear optical chromophores in accordance with various embodiments ofthe invention can be combined neat (i.e., without any addition of amatrix material or host polymer) with a solvent to form a lyotropiccomposition which provides at least partial self-alignment of thechromophores with additional shear to form a highly ordered and denselypacked state. In various embodiments, no further poling is required toprovide a nonlinear optical thin film suitable for use in electro-opticdevices, such as modulators. In various embodiments, the solvent can beremoved under controlled conditions to maintain the chromophore in thehighly ordered and densely packed state. In various embodiments,traditional poling processes including application of a field across thechromophore thin film can also be carried out. Nonlinear opticalchromophores in accordance with various embodiments of the invention canalso be combined with a matrix material or host polymer and a solvent toform a lyotropic composition. In various embodiments, a high boilingpoint solvent can be used for poling, such as in accordance with theprocesses described in provisional U.S. Pat. App. No. 63/264,880, filedon Dec. 3, 2021, the entire contents of which are incorporated herein byreference.

The first-order hyperpolarizability (β) is one of the most common anduseful NLO properties. Higher-order hyperpolarizabilities are useful inother applications such as all-optical (light-switching-light)applications. To determine if a material, such as a compound or polymer,includes a nonlinear optic chromophore with first-order hyperpolarcharacter and a sufficient electro-optic coefficient (r₃₃), which is afunction of β, the following test may be performed. First, the materialin the form of a thin film is placed in an electric field to align thedipoles. This may be performed by sandwiching a film of the materialbetween electrodes, such as indium tin oxide (ITO) substrates, goldfilms, or silver films, for example.

To generate a poling electric field, an electric potential is thenapplied to the electrodes while the material is heated to near its glasstransition (T_(g)) temperature. After a suitable period of time, thetemperature is gradually lowered while maintaining the poling electricfield. Alternatively, the material can be poled by corona poling method,where an electrically charged needle at a suitable distance from thematerial film provides the poling electric field. In either instance,the dipoles in the material tend to align with the field.

The nonlinear optical property of the poled material is then tested asfollows. Polarized light, often from a laser, is passed through thepoled material, then through a polarizing filter, and to a lightintensity detector. If the intensity of light received at the detectorchanges as the electric potential applied to the electrodes is varied,the material incorporates a nonlinear optic chromophore and has anelectro-optically variable refractive index. A more detailed discussionof techniques to measure the electro-optic constants of a poled filmthat incorporates nonlinear optic chromophores may be found in Chia-ChiTeng, Measuring Electro-Optic Constants of a Poled Film, in NonlinearOptics of Organic Molecules and Polymers, Chp. 7, 447-49 (Hari SinghNalwa & Seizo Miyata eds., 1997), incorporated by reference in itsentirety, except that in the event of any inconsistent disclosure ordefinition from the present application, the disclosure or definitionherein shall be deemed to prevail.

The relationship between the change in applied electric potential versusthe change in the refractive index of the material may be represented asits EO coefficient r₃₃. This effect is commonly referred to as anelectro-optic, or EO, effect. Devices that include materials that changetheir refractive index in response to changes in an applied electricpotential are called electro-optical (EO) devices.

The second-order hyperpolarizability (γ) or third-order susceptibility(χ⁽³⁾), are the normal measures of third-order NLO activity. While thereare several methods used to measure these properties, degenerate four-wave mixing (DFWM) is very common. See C. W. Thiel, “For- wave Mixingand Its Applications,“www.physics.montana.edu.students.thiel.docs/FWMixing.pdf the entirecontents of which are hereby incorporated herein by reference. Referringto Published U.S. Pat. Application No. US 2012/0267583A1, the entirecontents of which are incorporated herein by reference, a method ofevaluating third-order NLO properties of thin films, known in the art asDegenerate Four Wave Mixing (DFWM), can be used. In FIG. 4 of US2012/0267583A1, Beams 1 and 2 are picosecond, coherent pulses, absorbedby the NLO film deposited on a glass substrate. Beam 3 is a weaker,slightly delayed beam at the same wavelength as Beams 1 and 2. Beam 4 isthe resulting product of the wave mixing, diffracted off of thetransient holographic grating, produced by interferences of beams 1 and2 in the NLO material of the film. Beam 3 can be a “control” beam at atelecom wavelength which produces a “signal” beam at a frequency notabsorbed by the NLO material.

Nonlinear optical chromophores in accordance with the variousembodiments of the invention have the general formula (I):

wherein D represents an organic electron-donating group; A represents anorganic electron-accepting group having an electron affinity greaterthan the electron affinity of D; and II represents a II-bridge between Aand D. The terms electron-donating group (donor or “D”), II-bridge(bridging group or “II”), and electron-accepting group (acceptor or“A”), and general synthetic methods for forming D-II-A chromophores areknown in the art, for example as described in U.S. Pat. Nos. 5,670,091,5,679,763, 6,090,332, and 6,716,995, and U.S. Pat. App. No. 17/358,960,filed on Jun. 25, 2021, the entire contents of each of which isincorporated herein by reference.

An acceptor is an atom or group of atoms that has a low reductionpotential, wherein the atom or group of atoms can accept electrons froma donor through a II-bridge. The acceptor (A) has a higher electronaffinity that does the donor (D), so that, at least in the absence of anexternal electric field, the chromophore is generally polarized in theground state, with relatively more electron density on the acceptor (D).Typically, an acceptor group contains at least one electronegativeheteroatom that is part of a pi bond (a double or triple bond) such thata resonance structure can be drawn that moves the electron pair of thepi bond to the heteroatom and concomitantly decreases the multiplicityof the pi bond (i.e., a double bond is formally converted to single bondor a triple bond is formally converted to a double bond) so that theheteroatom gains formal negative charge. The heteroatom may be part of aheterocyclic ring. Exemplary acceptor groups include but are not limitedto —NO₂, —CN, —CHO, COR, CO₂R, —PO(OR)₃, —SOR, —SO₂R, and —SO₃R where Ris alkyl, aryl, or heteroaryl. The total number of heteroatoms andcarbons in an acceptor group is about 30, and the acceptor group may besubstituted further with alkyl, aryl, and/or heteroaryl.

Suitable electron-accepting groups “A” (also referred to in theliterature as electron-withdrawing groups) for nonlinear opticalchromophores in accordance with the various embodiments of the presentinvention include those described in published U.S. Pat. Applications:US 2007/0260062; US 2007/0260063; US 2008/0009620; US 2008/0139812; US2009/0005561; US 2012/0267583A1 (collectively referred to as “the priorpublications”), each of which is incorporated herein by reference in itsentirety; and in U.S. Pat. Nos.: 6,584,266; 6,393,190; 6,448,416;6,44,830; 6,514,434; 5,044,725; 4,795,664; 5,247,042; 5,196,509;4,810,338; 4,936,645; 4,767,169; 5,326,661; 5,187,234; 5,170,461;5,133,037; 5,106,211; and 5,006,285; and U.S. Pat. App. No. 17/358,960,filed on Jun. 25, 2021; each of which is also incorporated herein byreference in its entirety.

In various nonlinear optical chromophores in accordance with variouspreferred embodiments of the present invention, suitableelectron-accepting groups include those according to general formula(I^(a)):

wherein R² and R³ each independently represents a moiety selected fromthe group consisting of H, substituted or unsubstituted C₁-C₁₀ alkyl,substituted or unsubstituted C₂-C₁₀ alkenyl, substituted orunsubstituted C₂-C₁₀ alkynyl, substituted or unsubstituted aryl,substituted or unsubstituted alkylaryl, substituted or unsubstitutedcarbocyclic, substituted or unsubstituted heterocyclic, substituted orunsubstituted cyclohexyl, and (CH₂)_(n)—O—(CH₂)_(n) where n is 1-10. Asused herein,

represents a point of bonding to another portion of a larger molecularstructure. In various preferred embodiments, one or both of R² and R³represent a halogen-substituted moiety. Halogen-substituted may refer tomono-, di-, tri- and higher degrees of substitution. In variouspreferred embodiments, one of R² and R³ represent a halogen-substitutedalkyl moiety and the other represents an aromatic moiety. In variouspreferred embodiments, one of R² and R³ represent a halogen-substitutedaromatic moiety and the other represents an alkyl moiety. In variouspreferred embodiments, the electron-accepting group can be

In various preferred embodiments, the electron-accepting group can be

In various preferred embodiments, the electron-accepting group can be

A donor includes an atom or group of atoms that has a low oxidationpotential, wherein the atom or group of atoms can donate electrons to anacceptor “A” through a II-bridge. The donor (D) has a lower electronaffinity than does the acceptor (A), so that, at least in the absence ofan external electric field, the chromophore is generally polarized, withrelatively less electron density on the donor (D).

A donor in accordance with various embodiments of the present inventioncan include a tetrahydrocarbazole moiety represented by the generalformula (II):

wherein R¹ represents a moiety other than hydrogen, wherein R²represents a moiety selected from hydrogen, halides, alkoxy groups,alkyl groups (branched or unbranched), and aryl groups, wherein R³represents a moiety selected from hydrogen and alkyl groups (branched orunbranched), wherein R⁴ represents a moiety selected from hydrogen andalkyl groups (branched or unbranched), and wherein R⁵ which mayoptionally be present represents a fused aliphatic or aromatic ringhaving 3 to 5 carbon atoms. In various embodiments, R³ and R⁴ canrepresent the same moiety. In various embodiments R¹ represents a moietyselected from the group consisting of branched alkyl groups, and arylgroups. In various embodiments, R¹ represents a moiety selected fromsubstituted and unsubstituted benzyl groups.

A donor in accordance with various embodiments of the present inventioncan include a tetrahydrocarbazole moiety represented by the generalformula (IIa):

wherein R represents a moiety other than hydrogen.

In various embodiments, a donor can include a tetrahydrocarbazole moietyrepresented by the general formula (II), wherein R¹ represents anaryl-containing moiety. In various embodiments, R¹ can represent an arylgroup further substituted with a silyl group. In various embodiments, R¹can represent an aryl group further substituted with atriaryl-substituted silyl group. In various embodiments, R¹ canrepresents 4-(triphenylsilyl)-phenylmethyl.

In various embodiments, a donor can include a tetrahydrocarbazole moietyrepresented by the general formula (IIa), wherein R represents anaryl-containing moiety. In various embodiments, R can represent an arylgroup further substituted with a silyl group. In various embodiments, Rcan represent an aryl group further substituted with atriaryl-substituted silyl group. In various embodiments, R canrepresents 4-(triphenylsilyl)-phenylmethyl.

A “II-bridge” includes an atom or group of atoms through which electronsmay be delocalized from an electron donor (defined above) to an electronacceptor (defined above) through the orbitals of atoms in the bridge.Such groups are very well known in the art. Typically, the orbitals willbe p-orbitals on double (sp²) or triple (sp) bonded carbon atoms such asthose found in alkenes, alkynes, neutral or charged aromatic rings, andneutral or charged heteroaromatic ring systems. Additionally, theorbitals may be p-orbitals on atoms such as boron or nitrogen.Additionally, the orbitals may be p, d or f organometallic orbitals orhybrid organometallic orbitals. The atoms of the bridge that contain theorbitals through which the electrons are delocalized are referred tohere as the “critical atoms.” The number of critical atoms in a bridgemay be a number from 1 to about 30. The critical atoms may besubstituted with an organic or inorganic group. The substituent may beselected with a view toward improving the solubility of the chromophorein a polymer matrix, enhancing the stability of the chromophore, or forother purposes.

Suitable bridging groups (II) for nonlinear optical chromophoresaccording to general formula (I) of the present invention include thosedescribed in U.S. Pat. Nos.: 6,584,266; 6,393,190; 6,448,416; 6,44,830;6,514,434; and U.S. Pat. App. No. 17/358,960, filed on Jun. 25, 2021;each of which is also incorporated herein by reference in its entirety.

In various preferred embodiments, bridging groups (II) for nonlinearoptical chromophores according to general formula (I) of the presentinvention include those of the general formula (II^(a)):

wherein X represents a substituted or unsubstituted, branched orunbranched C₂-C₄ diyl moiety; wherein each a and b independentlyrepresents an integer of 0 to 3; and z represents an integer of 1 to 3.In various embodiments wherein a or b in general formula (II^(a)) is 1,that carbon-carbon double bond in the formula can be replaced with acarbon-carbon triple bond. Alternatively, in various preferredembodiments, bridging groups (II) for nonlinear optical chromophoresaccording to general formula (I) of the present invention include thoseof the general formula (II^(b)):

wherein X represents a substituted or unsubstituted, branched orunbranched C₂-C₄ diyl moiety. In various embodiments of the presentinvention wherein one or more diamondoid groups is covalently attachedto a bridging group according to general formulae II^(a) or II^(b), theone or more diamondoid groups may be bound, for example, to the sulfuror oxygen atoms of the thiophene group or to one or mor carbon atoms inX through an ether or thioether linkage.

In various preferred embodiments, bridging groups (II) for nonlinearoptical chromophores according to general formula (I) of the presentinvention include those of the general formula (II^(b)):

wherein each Y independently represents: a diamondoid-containing groupcovalently bound to the bridging group through any of the variouslinkages described herein below including but not limited to ether andthioether linkages; or each Y may represent a hydrogen, an alkyl group,aryl group, sulfur or oxygen linked akyl or aryl group, or a branched orunbranched, optionally heteroatom-containing C₁-C₄ substituent; whereineach a and b independently represents an integer of 0 to 3; z representsan integer of 1 to 3; and wherein each arc A independently represents asubstituted or unsubstituted C₂-C₄ alkyl group, which together with thecarbon bearing the Y substituent and its two adjacent carbon atoms formsa cyclic group. Substituted or unsubstituted C₂-C₄ alkyl groups whichconstitute arc A may include 1 to 4 hydrogen substituents eachcomprising a moiety selected from the group consisting of substituted orunsubstituted C₁-C₁₀ alkyl, substituted or unsubstituted C₂-C₁₀ alkenyl,substituted or unsubstituted C₂-C₁₀ alkynyl, substituted orunsubstituted aryl, substituted or unsubstituted alkylaryl, substitutedor unsubstituted carbocyclic, substituted or unsubstituted heterocyclic,substituted or unsubstituted cyclohexyl, and (CH₂)_(n)—O—(CH₂)_(n) wheren is 1-10. In various preferred embodiments, z represents 1. In variousembodiments according to the present invention, the electron-donatinggroup or electron-accepting group can include one or more covalentlybound diamondoid groups, and Y in general formula II^(c) may representany of the above substituents. In certain preferred embodiments, achromophore may include an electron-donating group including one or morecovalently linked diamondoid groups, preferably adamantyl, and thebridging group may include an isophorone group in accordance withgeneral formula II^(c) wherein Y represent an aryl thioethersubstituent.

In various preferred embodiments, bridging groups (II) for nonlinearoptical chromophores according to general formula (I) of the presentinvention include those of the general formula (II^(d)):

wherein each Y independently represents: a diamondoid-containing groupcovalently bound to the bridging group through any of the variouslinkages described herein below including but not limited to ether andthioether linkages; or each Y may represent a hydrogen, an alkyl group,aryl group, sulfur or oxygen linked alkyl or aryl group, an aryl group(optionally bearing a diamondoid group) linked directly by acarbon-carbon bond (e.g., adamantly anisole), a halogen, a halogenatedalkyl group, a halogenated aryl group, or a branched or unbranched,optionally heteroatom-containing C₁-C₄ substituent; wherein each a and bindependently represents an integer of 0 to 3; and z represents aninteger of 1 to 3. In various embodiments according to the presentinvention, the electron-donating group or electron-accepting group caninclude one or more covalently bound diamondoid groups, and Y in generalformula II^(d) may represent any of the above substituents. In certainpreferred embodiments, a chromophore may include an electron-donatinggroup including one or more covalently linked diamondoid groups,preferably adamantyl, and the bridging group may include an isophoronegroup in accordance with general formula II^(d) wherein Y represent anaryl thioether substituent. In various embodiments, each of the geminalmethyl groups on the isophorone bridge of the general formula II^(d) caninstead independently represent a moiety selected from the groupconsisting of substituted or unsubstituted C₁-C₁₀ alkyl, substituted orunsubstituted C₂-C₁₀ alkenyl, substituted or unsubstituted C₂-C₁₀alkynyl, substituted or unsubstituted aryl, substituted or unsubstitutedalky-laryl, substituted or unsubstituted carbocyclic, substituted orunsubstituted heterocyclic, substituted or unsubstituted cyclohexyl,halogens, halogenated alkyl groups (e.g., -CF₃), halogenated aryls andheteroaryl groups (e.g., pentafluorothiophenol), and(CH₂)_(n)—O—(CH₂)_(n) where n is 1-10.

For example, bridging groups (II) for nonlinear optical chromophoresaccording to general formula (I) of the present invention can include:

Examples of nonlinear optical chromophores according to variousembodiments can include:

Various embodiments according to the present invention include lyotropiccompositions comprising a nonlinear optical chromophore as disclosedherein and a solvent. Suitable solvents for lyotropic compositions inaccordance with various embodiments can include an aprotic, polarsolvent and mixtures thereof. In various embodiments, a suitable solventcan comprise propylene carbonate.

A suitable solvent(s) can be combined with a nonlinear opticalchromophore in any amount. In various embodiments, one or more solventscan be combined with a nonlinear optical chromophore in an amount of upto from about 25 wt.% to about 75 wt.%, and in various embodiments, fromabout 35 wt.% to about 65 wt.%, and in various embodiments from about 40wt.% to about 60 wt.%. In various embodiments, one or more solvents canbe combined with a nonlinear optical chromophore in an amount of up to50 wt.%.

Lyotropic compositions of a nonlinear optical chromophore and solvent inaccordance with the various embodiments of the invention exhibit atleast partial self-alignment. Such compositions can be efficiently poledwith minimal application of voltage. In various embodiments, lyotropiccompositions exhibit a high degree of self-alignment upon shearing suchthat poling with applied voltage is unnecessary. Lyotropic compositionsin accordance with various embodiments of the invention can form dense,highly packed, highly ordered thin films for use in electro-opticdevices. Thin films in accordance with various embodiments of theinvention can be formed without externally applied voltage, or withapplied voltage. In various embodiments, thin films are formed with noapplied voltage.

The invention will now be described in further detail with reference tothe following non-limiting example.

EXAMPLES Synthesis Example 1 Step 1: Synthesis ofTriphenyl(p-tolyl)silane

A dry RB flask (1) was charged with 1-bromo-4-methyl-benzene (9.93 mL,0.0807 mol) and THF (200 mL) then chilled to -78° C. in a dryice/acetone bath. n-Butyllithium (2.50 mol/L, 32.3 mL, 0.0807 mol) wasadded at a rate so the temperature did not rise above -55° C. (5 mLincrements), and the reaction was stirred under nitrogen at -78° C. for2 hours.

Another RB flask (2) was evacuated then filled with nitrogen 3 times,charged with triphenylsilyl chloride (26.2 g, 0.0888 mol),evacuated/filled with nitrogen 3 times, and stirred at 60° C. undervacuum for 1 H. The flask (2) was allowed to cool, filled with nitrogen,then charged with THF (100 mL) and chilled to -78° C.

The contents of flask 2 were cannulated into flask 1 at a steady drip,temperature increased 5° C. The reaction was stirred under nitrogen andallowed to slowly warm to room temperature.

The reaction was diluted with DCM, washed with water then brine, driedwith MgSO₄ and evaporated giving a white solid. It was stirred in hexanefor 1H, filtered/washed with hexane (500 mL).

Obtained triphenyl(p-tolyl)silane (25.4 g, 0.0725 mol, yield: 89.8%) asa white powder.

Step 2: Wohl-Ziegler Bromination of Triphenyl(p-tolyl)silane

A RB flask was charged with the triphenyl(p-tolyl)silane (0 mmol/L, 0mL, 0.0394 mol), N-Bromosuccinimide (7.36 g, 0.0413 mol), 400 mL of DCM,and 2-[(E)-(1-cyano-1-methyl-ethyl)azo]-2-methyl-propanenitrile (0.323g, 0.00197 mol). The reaction was refluxed under nitrogen overnight. TLCindicated quantitative conversion to the bromide.

The reaction was washed with water then brine, dried with MgSO4, andevaporated giving a tan powder. This was triturated in hexane andfiltered giving 3343-A, 13.8 g, and the filtrate was evaporated giving3343-H, 3.49 g. The hexane fraction was chromatographed, eluting withhexane/ethyl acetate (3-5%). The appropriate fractions were combined andevaporated giving 3343-frac-A-B. Fraction B was triturated in hexane andfiltered giving 3343-B as a very white granular powder, 885 mg.

Obtained [4-(bromomethyl)phenyl]-triphenyl-silane (14.7 g, 0.0342 mol,yield: 87.0%).

Step 3: Alkylation of 1,2,3,9-tetrahydrocarbazol-4-one

A RB flask was charged with [4-(bromomethyl)phenyl]-triphenyl-silane(13.8 g, 0.0321 mol), 1,2,3,9-tetrahydrocarbazol-4-one (5.95 g, 0.0321mol), and 200 mL DMF under nitrogen. The mixture was chilled to 0° C.then sodium hydride (60.0%, 1.41 g, 0.0353 mol) was added. The reactionwas stirred under nitrogen, slowly warming to RT. At 2H the reaction hadwarmed up and it was homogeneous, about 15 minutes later the productcrashed out and it stopped stirring. The reaction became a solid-lookingwhite paste.

The reaction was triturated in water then filtered/washed with water.The organics were chromatographed, eluting with hexane/ethyl acetate(5%). The appropriate fractions were combined and evaporated giving anoff white solid. It was dissolved in DCM, hexane was added and the DCMwas evaporated off. The resulting solids were filtered.

Obtained9-[(4-triphenylsilylphenyl)methyl]-2,3-dihydro-1H-carbazol-4-one (10.8g, 0.0202 mol, yield: 63.0%) as a white solid.

Step 4: Alkylation of9-[(4-triphenylsilylphenyl)methyl]-2,3-dihydro-1H-carbazol-4-one WithMethylmagnesium Bromide

A dry RB flask was charged with 9-benzyl-2,3-dihydro-1H-carbazol-4-one(6.18 g, 0.0224 mol) and 240 mL THF under nitrogen.Bromo(methyl)magnesium (3.00 mol/L, 15.0 mL, 0.0449 mol) was added, andthe reaction was stirred under nitrogen. After stirring over theweekend, the reaction was diluted with DCM, washed with water (Grignardevident on addition of water, acidified with HCl to eliminate emulsion),then brine, dried with MgSO4, and evaporated. The material waschromatographed, eluting with hexane/ethyl acetate (5%). The appropriatefractions were combined and evaporated.

Obtained 9-benzyl-4-methyl-2,3-dihydro-1H-carbazol-9-ium; bromide (2.19g, 0.00618 mol, yield: 27.5%).

Step 5: Reaction of donor, bridge and acceptor to form Chromophore 1. ARB flask was charged with(3E)-2-chloro-3-(hydroxymethylene)cyclohexene-1-carbaldehyde (0.403 g,0.00233 mol),2-[3-cyano-4-methyl-5-phenyl-5-(trifluoromethyl)-2-furylidene]propanedinitrile(0.736 g, 0.00233 mol), and 12 mL of methanol. It was stirred at 40° C.under nitrogen for 1 hour. The methanol was evaporated, then[4-[(4-methyl-2,3-dihydro-1H-carbazol-9-ium-9-yl)methyl]phenyl]-triphenyl-silane;bromide(1.43 g, 0.00233 mol) and 12 mL DCM were added. The reaction was stirredunder nitrogen at room temperature overnight. The reaction was added toa silica gel column and eluted with DCM. The appropriate fractions werecombined and evaporated, clean carbazolium was recovered, 3307-C, 391mg. The residue with product was chromatographed eluting with DCM. Theappropriate fractions were combined and evaporated giving 3307-P, 1.11g. It was triturated in hot methanol, allowed to cool, filtered, andwashed with methanol giving 3307-A, 0.752 g after drying. The methanolwas evaporated giving 3307-MeOH.

Obtained Chromophore 1:2-[4-[(E)-2-[(3Z)-2-chloro-3-[(2Z)-2-[9-[(4-triphenylsilylphenyl)methyl]-2,3-dihydro-1H-carbazol-4-ylidene]ethylidene]cyclohexen-1-yl]vinyl]-3-cyano-5-phenyl-5-(trifluoromethyl)-2-furylidene]propanedinitrile(1.11 g, 0.00113 mol, yield: 48.4%).

Synthesis Example 2

Using the donor group prepared in Synthesis Example1,9-benzyl-4-methyl-2,3-dihydro-1H-carbazol-9-ium; bromide, Chromophore2 was prepared as follows. A RB flask was charged with(3E)-2-chloro-3-(hydroxymethylene)-5-(trifluoromethyl)cyclohexene-1-carbaldehyde(0.349 g, 0.00145 mol),2-[3-cyano-4-methyl-5-phenyl-5-(trifluoromethyl)-2-furylidene]propanedinitrile(0.458 g, 0.00145 mol), and 12 mL of ethanol. It was stirred at 40° C.under nitrogen for 1 hour. The ethanol was evaporated, then[[4-[(4-methyl-2,3-dihydro-1H-carbazol-9-ium-9-yl)methyl]phenyl]-triphenyl-silane;bromide(809 mg, 0.00132 mol) and 12 mL DCM were added. The reaction was stirredunder nitrogen at room temperature overnight. The reaction was added toa silica gel column and eluted with DCM. The appropriate fractions werecombined and evaporated. The residue with product was chromatographedeluting with DCM. The appropriate fractions were combined andevaporated. This was triturated in hot methanol, allowed to cool,filtered, and washed with methanol.

Obtained2-[4-[(E)-2-[(3Z)-2-chloro-5-(trifluoromethyl)-3-[(2Z)-2-[9-[(4-triphenylsilylphenyl)methyl]-2,3-dihydro-1H-carbazol-4-ylidene]ethylidene]cyclohexen-1-yl]vinyl]-3-cyano-5-phenyl-5-(trifluoromethyl)-2-furylidene]propanedinitrile(0.595 g, 0.000566 mol, yield: 42.9%).

Examples of Maximal Absorption Wavelength for Chromophore Embodiments

Chromophore 1 was combined with propylene carbonate at 50% by weightforming a lyotropic composition. The composition was shear alignedbetween two glass substrates and subjected to light absorption analysisacross the visible and near infrared spectrum. Referring to FIG. 1 , ashear aligned sample (the curve with the absorption peak near 1200 nm)exhibited red-shift as shown by its peak values and overall shift in thenear infrared direction. As also shown in FIG. 1 , a shear alignedsample which was then heated to 150° C. for a brief period of time toremove solvent, did not exhibit such red-shift. Such red-shift isevidence of J-aggregate formation indicating at least partialself-alignment and anisotropy.

Chromophore 1 was combined with propylene carbonate at 50% by weightforming a lyotropic composition. The composition was placed between twoglass substrates and subjected to polarized light microscopy. Referringto FIGS. 2 a through 2 c , red color was readily observed in a shearaligned sample indicating J-aggregate formation, at least partialself-alignment and anisotropy. FIG. 2 c show a sample between two glasssubstrates prior to shear alignment. Notable micelle formation,evidencing lyotropic properties, is shown. In FIG. 2 b , a shear alignedsample evidences clear red color. Such red color evidences J-aggregateformation indicating at least partial self-alignment and anisotropy.FIG. 2 c , a sample subjected to heating at 100° C. to remove thesolvent shows no red coloration.

It will be appreciated by those skilled in the art that changes could bemade to the embodiments described above without departing from the broadinventive concept thereof. It is understood, therefore, that thisinvention is not limited to the particular embodiments disclosed, but itis intended to cover modifications within the spirit and scope of thepresent invention as defined by the appended claims.

What is claimed is:
 1. A lyotropic composition comprising the nonlinearoptical chromophore of the general formula (I):

wherein D represents an organic electron-donating group; A represents anorganic electron-accepting group having an electron affinity greaterthan the electron affinity of D; and Π represents a II-bridge between Aand D; wherein the electron-donating group D comprises atetrahydrocarbazole moiety bound to the Π-bridge at a carbon atom in thetetrahydro six-membered carbon ring of the tetrahydrocarbazole moiety,and wherein the hydrogen bound to the nitrogen of the five-membered ringof the carbazole moiety is replaced with a substituent R.
 2. Thenonlinear optical chromophore according to claim 1, wherein thetetrahydrocarbazole moiety is represented by the general formula (II):

wherein R represents a moiety other than hydrogen.
 3. The nonlinearoptical chromophore according to claim 2, wherein R represents a moietycomprising an aromatic ring.
 4. The nonlinear optical chromophoreaccording to claim 3, wherein R represents a moiety comprising anaromatic ring bearing a triaryl-substituted silyl substituent.
 5. Thenonlinear optical chromophore according to claim 4, wherein R representsa moiety of the general formula (III)

.
 6. The nonlinear optical chromophore according to claim 1, wherein Arepresents an electron-accepting group of the general formula (I^(a)):

wherein R² and R³ each independently represents a moiety selected fromthe group consisting of H, substituted or unsubstituted C₁-C₁₀ alkyl,substituted or unsubstituted C₂-C₁₀ alkenyl, substituted orunsubstituted C₂-C₁₀ alkynyl, substituted or unsubstituted aryl,substituted or unsubstituted alkylaryl, substituted or unsubstitutedcarbocyclic, substituted or unsubstituted heterocyclic, substituted orunsubstituted cyclohexyl, and (CH₂)_(n)—O—(CH₂)_(n) where n is 1-10. 7.The nonlinear optical chromophore according to claim 1, having thegeneral formula (IV)

wherein R represents a substituent other than hydrogen; wherein R² andR³ each independently represents a moiety selected from the groupconsisting of H, substituted or unsubstituted C₁-C₁₀ alkyl, substitutedor unsubstituted C₂-C₁₀ alkenyl, substituted or unsubstituted C₂-C₁₀alkynyl, substituted or unsubstituted aryl, substituted or unsubstitutedalkyl-aryl, substituted or unsubstituted carbocyclic, substituted orunsubstituted heterocyclic, substituted or unsubstituted cyclohexyl, and(CH₂)_(n)—O—(CH₂)_(n) where n is 1-10; wherein each Y independentlyrepresents: a hydrogen, a halogen, an alkyl group, aryl group, sulfur oroxygen linked alkyl or aryl group, or a branched or unbranched,optionally heteroatom-containing C₁-C₄ substituent; wherein each a and bindependently represents an integer of 0 to 3; z represents an integerof 1 to 3; and wherein each arc A independently represents a substitutedor unsubstituted C₂-C₄ alkyl group, which together with the carbonbearing the Y substituent and its two adjacent carbon atoms forms acyclic group.
 8. The lyotropic composition of claim 1, furthercomprising one or more aprotic, polar solvents.
 9. The lyotropiccomposition according to claim 8, wherein the one or more aprotic, polarsolvents comprise propylene carbonate.
 10. A thin film prepared from thecomposition according to claim
 8. 11. The thin film of claim 10, whereinthe film is prepared by removal of the one or more solvents from thecomposition while the nonlinear optical chromophore is in a highlyordered and densely packed state.
 12. An electro-optic device comprisingthe thin film according to claim 11.